After the conclusion of the current ozone season, this page will provide daily peak 8-hour-averaged ozone concentrations as measured at MassDEP monitors across Massachusetts between April and September, color-coded according to health-based Air Quality Index categories.  See Ozone Health Guidelines for an explanation of the colors.

Data and summary information for past years:

2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001